| #!/usr/bin/python |
| # |
| # Copyright (C) 2016 Google, Inc |
| # Written by Simon Glass <sjg@chromium.org> |
| # |
| # SPDX-License-Identifier: GPL-2.0+ |
| # |
| |
| import struct |
| import sys |
| |
| import fdt_util |
| |
| # This deals with a device tree, presenting it as an assortment of Node and |
| # Prop objects, representing nodes and properties, respectively. This file |
| # contains the base classes and defines the high-level API. Most of the |
| # implementation is in the FdtFallback and FdtNormal subclasses. See |
| # fdt_select.py for how to create an Fdt object. |
| |
| # A list of types we support |
| (TYPE_BYTE, TYPE_INT, TYPE_STRING, TYPE_BOOL) = range(4) |
| |
| def CheckErr(errnum, msg): |
| if errnum: |
| raise ValueError('Error %d: %s: %s' % |
| (errnum, libfdt.fdt_strerror(errnum), msg)) |
| |
| class PropBase: |
| """A device tree property |
| |
| Properties: |
| name: Property name (as per the device tree) |
| value: Property value as a string of bytes, or a list of strings of |
| bytes |
| type: Value type |
| """ |
| def __init__(self, node, offset, name): |
| self._node = node |
| self._offset = offset |
| self.name = name |
| self.value = None |
| |
| def GetPhandle(self): |
| """Get a (single) phandle value from a property |
| |
| Gets the phandle valuie from a property and returns it as an integer |
| """ |
| return fdt_util.fdt32_to_cpu(self.value[:4]) |
| |
| def Widen(self, newprop): |
| """Figure out which property type is more general |
| |
| Given a current property and a new property, this function returns the |
| one that is less specific as to type. The less specific property will |
| be ble to represent the data in the more specific property. This is |
| used for things like: |
| |
| node1 { |
| compatible = "fred"; |
| value = <1>; |
| }; |
| node1 { |
| compatible = "fred"; |
| value = <1 2>; |
| }; |
| |
| He we want to use an int array for 'value'. The first property |
| suggests that a single int is enough, but the second one shows that |
| it is not. Calling this function with these two propertes would |
| update the current property to be like the second, since it is less |
| specific. |
| """ |
| if newprop.type < self.type: |
| self.type = newprop.type |
| |
| if type(newprop.value) == list and type(self.value) != list: |
| self.value = [self.value] |
| |
| if type(self.value) == list and len(newprop.value) > len(self.value): |
| val = self.GetEmpty(self.type) |
| while len(self.value) < len(newprop.value): |
| self.value.append(val) |
| |
| def BytesToValue(self, bytes): |
| """Converts a string of bytes into a type and value |
| |
| Args: |
| A string containing bytes |
| |
| Return: |
| A tuple: |
| Type of data |
| Data, either a single element or a list of elements. Each element |
| is one of: |
| TYPE_STRING: string value from the property |
| TYPE_INT: a byte-swapped integer stored as a 4-byte string |
| TYPE_BYTE: a byte stored as a single-byte string |
| """ |
| size = len(bytes) |
| strings = bytes.split('\0') |
| is_string = True |
| count = len(strings) - 1 |
| if count > 0 and not strings[-1]: |
| for string in strings[:-1]: |
| if not string: |
| is_string = False |
| break |
| for ch in string: |
| if ch < ' ' or ch > '~': |
| is_string = False |
| break |
| else: |
| is_string = False |
| if is_string: |
| if count == 1: |
| return TYPE_STRING, strings[0] |
| else: |
| return TYPE_STRING, strings[:-1] |
| if size % 4: |
| if size == 1: |
| return TYPE_BYTE, bytes[0] |
| else: |
| return TYPE_BYTE, list(bytes) |
| val = [] |
| for i in range(0, size, 4): |
| val.append(bytes[i:i + 4]) |
| if size == 4: |
| return TYPE_INT, val[0] |
| else: |
| return TYPE_INT, val |
| |
| def GetEmpty(self, type): |
| """Get an empty / zero value of the given type |
| |
| Returns: |
| A single value of the given type |
| """ |
| if type == TYPE_BYTE: |
| return chr(0) |
| elif type == TYPE_INT: |
| return struct.pack('<I', 0); |
| elif type == TYPE_STRING: |
| return '' |
| else: |
| return True |
| |
| def GetOffset(self): |
| """Get the offset of a property |
| |
| This can be implemented by subclasses. |
| |
| Returns: |
| The offset of the property (struct fdt_property) within the |
| file, or None if not known. |
| """ |
| return None |
| |
| class NodeBase: |
| """A device tree node |
| |
| Properties: |
| offset: Integer offset in the device tree |
| name: Device tree node tname |
| path: Full path to node, along with the node name itself |
| _fdt: Device tree object |
| subnodes: A list of subnodes for this node, each a Node object |
| props: A dict of properties for this node, each a Prop object. |
| Keyed by property name |
| """ |
| def __init__(self, fdt, offset, name, path): |
| self._fdt = fdt |
| self._offset = offset |
| self.name = name |
| self.path = path |
| self.subnodes = [] |
| self.props = {} |
| |
| def _FindNode(self, name): |
| """Find a node given its name |
| |
| Args: |
| name: Node name to look for |
| Returns: |
| Node object if found, else None |
| """ |
| for subnode in self.subnodes: |
| if subnode.name == name: |
| return subnode |
| return None |
| |
| def Scan(self): |
| """Scan the subnodes of a node |
| |
| This should be implemented by subclasses |
| """ |
| raise NotImplementedError() |
| |
| def DeleteProp(self, prop_name): |
| """Delete a property of a node |
| |
| This should be implemented by subclasses |
| |
| Args: |
| prop_name: Name of the property to delete |
| """ |
| raise NotImplementedError() |
| |
| class Fdt: |
| """Provides simple access to a flat device tree blob. |
| |
| Properties: |
| fname: Filename of fdt |
| _root: Root of device tree (a Node object) |
| """ |
| def __init__(self, fname): |
| self._fname = fname |
| |
| def Scan(self, root='/'): |
| """Scan a device tree, building up a tree of Node objects |
| |
| This fills in the self._root property |
| |
| Args: |
| root: Ignored |
| |
| TODO(sjg@chromium.org): Implement the 'root' parameter |
| """ |
| self._root = self.Node(self, 0, '/', '/') |
| self._root.Scan() |
| |
| def GetRoot(self): |
| """Get the root Node of the device tree |
| |
| Returns: |
| The root Node object |
| """ |
| return self._root |
| |
| def GetNode(self, path): |
| """Look up a node from its path |
| |
| Args: |
| path: Path to look up, e.g. '/microcode/update@0' |
| Returns: |
| Node object, or None if not found |
| """ |
| node = self._root |
| for part in path.split('/')[1:]: |
| node = node._FindNode(part) |
| if not node: |
| return None |
| return node |
| |
| def Flush(self): |
| """Flush device tree changes back to the file |
| |
| If the device tree has changed in memory, write it back to the file. |
| Subclasses can implement this if needed. |
| """ |
| pass |
| |
| def Pack(self): |
| """Pack the device tree down to its minimum size |
| |
| When nodes and properties shrink or are deleted, wasted space can |
| build up in the device tree binary. Subclasses can implement this |
| to remove that spare space. |
| """ |
| pass |
